Author Topic: GT 40 heads idenification help please  (Read 1941 times)

gblue

  • Newbie
  • *
  • Posts: 5
    • View Profile
GT 40 heads idenification help please
« on: August 26, 2020, 07:25:02 PM »

How do I tell if the heads are from a 1965-1966 GT 40 rather than stock heads........previous owner say that's what he was told.
would they have a special code or other marking?

Thanks,

Gregg

S7MS427

  • Sr. Member
  • ****
  • Posts: 303
    • View Profile
    • S-Tech Enterprises, LLC
Re: GT 40 heads idenification help please
« Reply #1 on: August 26, 2020, 09:05:39 PM »
If I'm not mistaken, smallblock GT40 heads are identified by casting number C6FE-6090 A and are cast iron. They are similar to Hi-Po heads in that they have cast in pockets for the valve springs.  I'm not sure if they use guide plates or if they have the close tolerance push rod slots.  Check them out at: http://mustangtek.com/heads/C6FE-6090-A.html.  I'm sure others will correct any inacuratcies in my statement.
Roy Simkins
http://www.S-TechEnt.com/Shelby.htm
1966 G.T.350H SFM6S817
1967 G.T.500 67400F7A03040

Bob Gaines

  • SAAC Member
  • Hero Member
  • *
  • Posts: 7147
  • Original Posts:14706
    • View Profile
Re: GT 40 heads idenification help please
« Reply #2 on: August 26, 2020, 09:53:05 PM »
If I'm not mistaken, smallblock GT40 heads are identified by casting number C6FE-6090 A and are cast iron. They are similar to Hi-Po heads in that they have cast in pockets for the valve springs.  I'm not sure if they use guide plates or if they have the close tolerance push rod slots.  Check them out at: http://mustangtek.com/heads/C6FE-6090-A.html.  I'm sure others will correct any inacuratcies in my statement.
+1
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

shelbydoug

  • SAAC Member
  • Hero Member
  • *
  • Posts: 5414
    • View Profile
Re: GT 40 heads idenification help please
« Reply #3 on: August 27, 2020, 07:09:19 AM »
I think that part of the issue is the re-use of the name GT40 heads by Ford on their production heads in the '90s.

Thanks Ford.
68 GT350 Lives Matter!

gt350hr

  • Hero Member
  • *****
  • Posts: 2489
  • Randy Gillis in real life - 5353 original posts
    • View Profile
Re: GT 40 heads idenification help please
« Reply #4 on: August 27, 2020, 11:42:19 AM »
    Roy,
      There are two "original versions" of the C6FE iron ,289 , GT40 head. Type one is as you mentioned with cast in spring pockets like a HiPo. Type two does not have the cast in pockets. This isn't a simple machining thing , it was a revision to the casting. Neither used guide plates as the guide was in the pushrod passage. "Originally" the 1.875 dia intake valves used a 30* seat angle and the 1.625 exhaust valve used the more common 45* angle. The casting number is on the outside ( all) as well as the inside ( on many , but not "all"). They all use a conventional 289 HiPo stud and rocker arm assembly. The combustion chamber is also revised and is larger in volume than a HiPo head. The ones from SAI had the "banana water ports" welded up. Ford and Bud Moore didn't do this modification. The heads are prone to external cracking just above the lower bolt holes. It is common to see them repaired and the repair if done right is bulletproof.
   The heads were reproduced in the 90's and "289" was added in the valley area. If it is there or you can see that it "was" there , you have a repop head. Those head casting cores are now owned by Cobra Automotive and have had all the "issues" corrected. "New" ones are virtually the same cost as used ones but are FAR superior. I have owned 7 sets of originals in the past . They ranged from NOS to those ported by Valley Head Service and Mondello. I am looking forward to a new set from Cobra Automotive.
    Randy.
Celebrating 46 years of drag racing 6S477 and no end in sight.

S7MS427

  • Sr. Member
  • ****
  • Posts: 303
    • View Profile
    • S-Tech Enterprises, LLC
Re: GT 40 heads idenification help please
« Reply #5 on: August 27, 2020, 12:50:40 PM »
    Roy,
      There are two "original versions" of the C6FE iron ,289 , GT40 head. Type one is as you mentioned with cast in spring pockets like a HiPo. Type two does not have the cast in pockets. This isn't a simple machining thing , it was a revision to the casting. Neither used guide plates as the guide was in the pushrod passage. "Originally" the 1.875 dia intake valves used a 30* seat angle and the 1.625 exhaust valve used the more common 45* angle. The casting number is on the outside ( all) as well as the inside ( on many , but not "all"). They all use a conventional 289 HiPo stud and rocker arm assembly. The combustion chamber is also revised and is larger in volume than a HiPo head. The ones from SAI had the "banana water ports" welded up. Ford and Bud Moore didn't do this modification. The heads are prone to external cracking just above the lower bolt holes. It is common to see them repaired and the repair if done right is bulletproof.
   The heads were reproduced in the 90's and "289" was added in the valley area. If it is there or you can see that it "was" there , you have a repop head. Those head casting cores are now owned by Cobra Automotive and have had all the "issues" corrected. "New" ones are virtually the same cost as used ones but are FAR superior. I have owned 7 sets of originals in the past . They ranged from NOS to those ported by Valley Head Service and Mondello. I am looking forward to a new set from Cobra Automotive.
    Randy.

Randy,

Great info as always.  I'm always interested in knowing more and have been fascinated by these heads for years.  I thought the chamber was something like a 351W in shape.  Is this correct?  An engine with these heads and a C7FE LeMans cam would be fun to build.  It would be tempting to invest in a set of the new Cobra Automotive heads, but they have no place on a Hertz car with a stock 289 Hi-Po and a C4.

Thanks again for your insight.
Roy Simkins
http://www.S-TechEnt.com/Shelby.htm
1966 G.T.350H SFM6S817
1967 G.T.500 67400F7A03040

gt350hr

  • Hero Member
  • *****
  • Posts: 2489
  • Randy Gillis in real life - 5353 original posts
    • View Profile
Re: GT 40 heads idenification help please
« Reply #6 on: August 27, 2020, 01:58:52 PM »
   Thanks Roy! I have been fortunate to have owned two of the original engines one used the ultra rare C6FE two bolt main block and the other was an SK numbered four bolt ( pre tunnel port /Boss) Both had the LeMans cam (C7FE) in them. That was the best Ford had at the time. Sadly virtually any modern aluminum head will out perform them at a fraction of the cost.
   Randy
Celebrating 46 years of drag racing 6S477 and no end in sight.

john galt

  • Jr. Member
  • **
  • Posts: 35
    • View Profile
Re: GT 40 heads idenification help please
« Reply #7 on: August 27, 2020, 05:54:35 PM »
For those who might be interested:  One idiosyncrasy specific to the original 1960ís FoMoCo C6FE 289 cylinder heads was the bolt hole to the right side of each exhaust port was drilled through into the water jacket.  Back in the day, after seeing water seeping out near several exhaust ports, more than one mechanic concluded the head was cracked.

The preferred cure was to install a short set screw (with sealant) deep under the header bolt, or apply sealant to the header bolt threads.

As Randy correctly posted, cracks in original C6FE heads were quite common.  Usually, the cracks occurred at the lower outer corners of the head. 

98SVT - was 06GT

  • SAAC Member
  • Hero Member
  • *
  • Posts: 2902
    • View Profile
Re: GT 40 heads idenification help please
« Reply #8 on: August 27, 2020, 10:11:26 PM »
I know a guy who is looking for a pair if anyone has some to sell. Yes he knows the value and has the money.
Previous owner 6S843 - GT350H & 68 GT500 Convert #135.
Mine: GT1 Mustang Track Toy, 1998 SVT Cobra, Wife's: 2004 Tbird
Member since 1975 - priceless

gt350hr

  • Hero Member
  • *****
  • Posts: 2489
  • Randy Gillis in real life - 5353 original posts
    • View Profile
Re: GT 40 heads idenification help please
« Reply #9 on: August 28, 2020, 11:23:15 AM »
  Jay ( Cushman Competition) usually has a pair for sale. Others pop up from time to time.



   John , the redesign of the head didn't require a new "tape control" ( pre CNC , LOL) machining program , so the same one used for 289HP heads was used. The new internal core patterns were a little off and the drilling and tapping process broke through as you mentioned. Yes the "factory fix" was the short set screw and "pipe dope" for sealant.
Celebrating 46 years of drag racing 6S477 and no end in sight.